THE VALUE OF CERVICAL LENGTH TO PREDICT PRETERM BIRTH
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www.wjpr.net Vol 8, Issue 7, 2019. 1706 THE VALUE OF CERVICAL LENGTH TO PREDICT PRETERM BIRTH Alhan Hussien Abod and Maha Abdulameer Oudah* Ministry of Health - Baghdad Medical office, Al-Karkh, Al Ameel Secter, Health Center Associations, Baghdad, Iraq. Ministry of Health, Baghdad, Iraq. ABSTRACT The ultrasound-based measurement ın the 1980s was developed to identify women at increased risk of preterm birth. The risk of preterm birth was inversely correlated to the length of the cervix as measured by ultrasound. This observation has been confirmed in multiple studies using different techniques; however, the most widely accepted and used technique is transvaginal ultrasound.34,47–57 A number of interventions based on this observation have been studied in randomized trials. A recent meta-analysis58 has looked at its efficacy in preventing preterm birth. Since the publication of the 2001 SOGC guideline, 36 there have been numerous studies on imaging, natural history, and use of transvaginal ultrasound in common clinical scenarios, as well as a number of randomized trials looking at interventions for a short cervix. This updated guideline provides a comprehensive review of studies of shortened cervical length diagnosed on transvaginal ultrasound and is broader in scope than the 2001 guideline. KEYWORDS: Ultrasound - Cervical length - population - preterm - Transvaginal -Preterm birth. INTRODUCTION Cervical length in the general obstetrical population is relatively stable over the first 2 trimesters. The natural history of cervical length change may be useful in identifying women at increased risk of spontaneous preterm birth. World Journal of Pharmaceutical Research SJIF Impact Factor 8.074 Volume 8, Issue 7, 1706-1718. Research Article ISSN 2277– 7105 *Corresponding Author Dr. Maha Abdulameer Oudah Ministry of Health, Baghdad, Iraq. Article Received on 11 April 2019, Revised on 01 May 2019, Accepted on 21 May 2019 DOI: 10.20959/wjpr20197-15101
THE VALUE OF CERVICAL LENGTH TO PREDICT PRETERM BIRTH
Oudah et al. World Journal of Pharmaceutical Research
1706
BIRTH
Alhan Hussien Abod and Maha Abdulameer Oudah*
Ministry of Health - Baghdad Medical office, Al-Karkh, Al Ameel
Secter, Health Center
Associations, Baghdad, Iraq.
ABSTRACT
The ultrasound-based measurement n the 1980s was developed to
identify women at increased risk of preterm birth. The risk of
preterm
birth was inversely correlated to the length of the cervix as
measured
by ultrasound. This observation has been confirmed in multiple
studies
using different techniques; however, the most widely accepted
and
used technique is transvaginal ultrasound.34,47–57 A number
of
interventions based on this observation have been studied in
randomized trials. A recent meta-analysis58 has looked at its
efficacy
in preventing preterm birth. Since the publication of the 2001
SOGC
guideline, 36 there have been numerous studies on imaging,
natural
history, and use of transvaginal ultrasound in common clinical
scenarios, as well as a number
of randomized trials looking at interventions for a short cervix.
This updated guideline
provides a comprehensive review of studies of shortened cervical
length diagnosed on
transvaginal ultrasound and is broader in scope than the 2001
guideline.
KEYWORDS: Ultrasound - Cervical length - population - preterm -
Transvaginal -Preterm
birth.
INTRODUCTION
Cervical length in the general obstetrical population is relatively
stable over the first 2
trimesters. The natural history of cervical length change may be
useful in identifying women
at increased risk of spontaneous preterm birth.
World Journal of Pharmaceutical Research SJIF Impact Factor
8.074
Volume 8, Issue 7, 1706-1718. Research Article ISSN 2277–
7105
*Corresponding Author
Revised on 01 May 2019, Accepted on 21 May 2019
DOI: 10.20959/wjpr20197-15101
Oudah et al. World Journal of Pharmaceutical Research
1707
Because there may be different patterns or a delay in cervical
length shortening, repeat
assessment of cervical length may be useful. (II-2). [2]
There is no consensus on the optimal
timing or frequency of serial evaluations of cervical length. If
repeat measurements are
performed, they should be done at suitable intervals to minimize
the likelihood of observation
error. (II-2). [3]
Transvaginal sonography can be used to assess the risk of preterm
birth in women with a
history of spontaneous preterm birth and to differentiate those at
higher and lower risk of
preterm delivery. The gestational age of a prior preterm birth
affects the cervical length in a
future pregnancy. (II–2). [4]
Cervical length measurement can be used to identify increased risk
of preterm birth in
asymptomatic women at 24 weeks’ gestation who are at increased risk
of preterm birth (e.g.,
those who have a history of prior spontaneous preterm birth,
previous excisional treatment for
cervical dysplasia, uterine anomaly, or prior multiple dilatation
and evacuation procedures
beyond 13 weeks’ gestation) and who have a short cervical
length.
This information may help with empiric management of these women,
including reduction of
activity level, work, or travel, relocation, increased
surveillance, and administration of
corticosteroids. (III). [6]
Transvaginal ultrasound appears to be safe in preterm premature
rupture of membranes, but
its clinical predictive value is uncertain in this context. (II-2).
[7]
It is unclear whether ultrasonographic cervical length assessment
has significant advantages
over clinical examination alone after elective or emergency
cervical cerclage placement,
although some signs, such as funneling to the stitch, are
associated with a high risk of preterm
premature rupture of membranes. There is no consensus on the
frequency or timing of
ultrasonographic cervical length assessment post cerclage. (II-2).
[8]
It is unclear whether a
policy of cervical length surveillance is equivalent to clinical
assessment of the need for
elective cerclage in those at risk of preterm delivery.(I).
[9]
Ultrasonographic cervical length assessment and fetal fibronectin
appear to be similar in
predictive ability, and the combination of both in a high-risk
population may be of value.
However, further research is needed in this area. (II-2)
Recommendations 1. Transabdominal
ultrasonography should not be used for cervical length assessment
to predict preterm birth.
(II-2D) 2.
Oudah et al. World Journal of Pharmaceutical Research
1708
Transvaginal ultrasonography is the preferred route for cervical
assessment to identify
women at increased risk of spontaneous preterm birth and may be
offered to women at
increased risk of preterm birth. (II-2B) 3.
Transperineal ultrasonography may be offered to women at increased
risk of preterm birth if
transvaginal ultrasonography is either unacceptable or unavailable.
(II-2B) 4. Because of poor
positive predictive values and sensitivities and lack of proven
effective interventions, routine
transvaginal cervical length assessment is not recommended in women
at low risk. (II-2E) 5.
In women presenting with suspected preterm labor, transvaginal
sonographic assessment of
cervical length may be used to help in determining who is at high
risk of preterm delivery and
may be helpful in preventing unnecessary intervention.
It is unclear whether this information results in a reduced risk of
preterm birth. (II-2B) 6. In
asymptomatic women with a history of spontaneous preterm birth and
an
ultrasonographically diagnosed short cervical length.
Objectives
birth.
(2) interventions associated with a short cervical length.
Outcomes: Reduction in rates of
prematurity and/or better identification of those at risk, as well
as possible prevention of
unnecessary interventions.
MATERIALS AND METHODS
Preterm birth is the leading cause of perinatal morbidity and
mortality.1–5 Despite advances
in perinatal care, the incidence of preterm birth continues to
rise, primarily because of the
increased multiple pregnancies resulting from assisted
reproduction.6–9 Tocolytics prolong
pregnancy minimally once preterm labor has begun, and they can be
associated with
significant undesirable maternal, fetal, and neonatal
consequences.10–19 In order to address
the prematurity problem, it is important to identify those at
increased risk.
The following are risk factors for spontaneous preterm birth
Reproductive history (previous spontaneous preterm birth and use of
assisted reproductive
technologies). [8,20-22]
Oudah et al. World Journal of Pharmaceutical Research
1709
uterine anomalies, [22]
neoplasia). [23-250]
a prior preterm birth [27]
)
• Demographic factors (low socioeconomic status, single marital
status, low level of
education, First Nations ethnicity, or maternal age 35 years)
)
• Inadequate prenatal care, low pre-pregnancy weight and poor
weight gain in pregnancy. [29]
However, many women who deliver preterm do not have any known risk
factors. [8,22]
Research has focused on combined risk scoring systems that use
multiple serum markers,
ultrasound, and maternal demographic factors, but these have not
been fully validated in large
scale studies. [30-42]
biochemical markers such as fetal fibronectin and screening for
infections. [27,43-46]
In the 1980s, an objective, ultrasound-based measurement was
developed to identify women
at increased risk of preterm birth. The risk of preterm birth was
inversely correlated to the
length of the cervix as measured by ultrasound.
This observation has been confirmed in multiple studies using
different techniques; however,
the most widely accepted and used technique is transvaginal
ultrasound. [34,47-57]
A number of
interventions based on this observation have been studied in
randomized trials.
A recent meta-analysis58 has looked at its efficacy in preventing
preterm birth. Since the
publication of the 2001 SOGC guideline,36 there have been numerous
studies on imaging,
natural history, and use of transvaginal ultrasound in common
clinical scenarios, as well as a
number of randomized trials looking at interventions for a short
cervix.
This updated guideline provides a comprehensive review of studies
of shortened cervical
length diagnosed on transvaginal ultrasound and is broader in scope
than the 2001 guideline,
as shown n table (1) below.
www.wjpr.net Vol 8, Issue 7, 2019.
Oudah et al. World Journal of Pharmaceutical Research
1710
Digital assessment of the cervix has been commonly used to diagnose
premature labor or to
evaluate women perceived to be at increased risk of preterm labor.
Digital assessment of
cervical length is subjective, varies between Table 1. Key to
evidence statements and grading
of recommendations, using the ranking of the Canadian Task Force on
Preventive Health
Care Quality of evidence assessment* Classification of
recommendations† I: Evidence
obtained from at least one properly randomized controlled trial
A.
There is good evidence to recommend the clinical preventive action
II-1: Evidence from
well-designed controlled trials without randomization B. There is
fair evidence to recommend
the clinical preventive action II-2: Evidence from well–designed
cohort (prospective or
retrospective) or case-control studies, preferably from more than
one center or research group
C.
The existing evidence is conflicting and does not allow to make a
recommendation for or
against use of the clinical preventive action; however, other
factors may influence decision-
making II-3: Evidence obtained from comparisons between times or
places with or without
the intervention. Dramatic results in uncontrolled experiments
(such as the results of
treatment with penicillin in the 1940s) could also be included in
this category D.
There is fair evidence to recommend against the clinical preventive
action E. There is good
evidence to recommend against the clinical preventive action III:
Opinions of respected
authorities, based on clinical experience, descriptive studies, or
reports of expert committees
L.
Oudah et al. World Journal of Pharmaceutical Research
1711
There is insufficient evidence (in quantity or quality) to make a
recommendation; however,
other factors may influence decision-making * The quality of
evidence reported in these
guidelines has been adapted from The Evaluation of Evidence
criteria described in the
Canadian Task Force on Preventive Health Care. 141 †
Recommendations included in these
guidelines have been adapted from the Classification of
Recommendations criteria described
in The Canadian Task Force on Preventive Health Care. 141 MAY JOGC
MAI 2011 l 489
Ultrasonographic Cervical Length Assessment in Predicting Preterm
Birth in Singleton
Pregnancies examiners, and underestimates true anatomic length. In
one study, digital
examinations before hysterectomy underestimated cervical length by
approximately 14 mm,
whereas ultrasonography measured length accurately. [59]
Investigations using transvaginal
cervical length. [57,60]
This underestimation may result from an inability to assess the
cervix length digitally beyond
the vaginal fornices unless there is 2 cm or more of dilatation and
the entire intracervical
canal is examined.
The majority of studies have found that ultrasound assessment of
cervical length is superior
to clinical examination for the prediction of preterm birth.
[61–64]
Therefore, ultrasound
assessment of cervical length is more reliable and more clinically
predictive of preterm birth
than manual examination of the cervix.
Comparson of Transvagnal, Transabdomnal, and Transperneal
Ultrasonographc
Cervcal Length Assessment
disadvantages led to a preference for transvaginal ultrasound
assessment. Both TP and TV
cervical assessments have been studied, with most studies
evaluating TV assessment. [65,66]
The patient’s bladder must be full for transabdominal
ultrasonography to assess the cervix
adequately, but this may spuriously lengthen the cervix by opposing
the anterior and posterior
lower uterine segments [65]
and concealing cervical shortening or funneling.
In contrast, TV ultrasound is performed with the bladder empty.
[66]
Transabdominal
ultrasound is significantly less likely than the other 2 methods to
provide adequate imaging
and measurements. [67]
Oudah et al. World Journal of Pharmaceutical Research
1712
Visualization of the cervix by transabdominal ultrasonography is
hampered significantly by
maternal obesity, shadowing from fetal parts, and the need for
lower frequency transducers.
Normal Cervcal Length: Cervical length is normally distributed and
remains relatively
constant in pregnancy until the third trimester. [73-75]
If there is any statistically significant
reduction in length, it is not clinically significant.
The natural history of cervical shortening in women who will
deliver preterm may be used to
determine when serial measurements should be performed.
These studies may make it possible to time reassessment and perhaps
stratify follow-up
according to length of measurement and the desired target threshold
for intervention. Studies
report thresholds for intervention ranging from 15 mm to 25 mm.
[82-87]
Thus depending on the initial cervical length, the chosen threshold
for intervention, and
knowledge of natural history, it is possible to estimate when the
next measurement should be
performed. For example, if the measured cervical length is 36 mm
and the threshold for
intervention is 20 mm, then it is reasonable to wait 2 weeks to
reassess cervical length,
assuming the greatest velocity of cervical decline (8
mm/week).
Using a mid-range estimate of cervical decline (5 mm/week), it
would be reasonable to wait
at least 3 weeks between ultrasound assessments. If the initial
cervical length is greater than
that, the interval between assessments could be longer. As shown n
table (2).
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Oudah et al. World Journal of Pharmaceutical Research
1713
As abvous of infection and should be postponed until labor is
established. Several cohort
studies have shown that the cervical length measured by TV predicts
latency to delivery in
preterm premature rupture of membranes.109,110 In a much smaller
study, cervical length
measurements by TP ultrasound did not correlate with latency
duration to delivery.111
Transvaginal cervical length measurement in a randomized trial was
not found to increase the
risk of infection in patients with preterm premature rupture of
membranes. This study did not
find that cervical length had predictive value for latency.
CONCLUSION
Ultrasonographic cervical measurement is a safe and effective
technique to predict increased
risk of preterm delivery in selected women. The transvaginal route
appears to be the most
well studied and is acceptable to women; however, the transperineal
route can also be used if
the patient declines the transvaginal route. It can also be used to
prevent unnecessary
interventions in women at increased risk of preterm delivery if the
result is reassuring. In
contrast, routine prenatal transvaginal ultrasound screening of
cervical length in low-risk
populations is not supported by available evidence. Evidence from
randomized trials supports
the recommendation of cerclage in patients with a prior preterm
birth and a short cervix. The
thresholds proposed vary from 15 mm to 28 mm. The use of
progesterone in patients with a
short cervix appears promising, but consensus recommendation awaits
further evidence
and/or analysis. Further evidence is also needed with respect to
the utility of measuring fetal
fibronectin in conjunction with measurements of cervical
length.
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